A POS (point of sale) terminal is a multi-functional terminal. When the POS is installed in a specially-engaged commercial unit or an accepting site of credit cards and connected with a computer to form a network, it can achieve automatic electronic funds transfer. The POS terminal supports functions such as consumption, pre-authorization, balance enquiry, transfer, and so on, and is secure, convenient and reliable to use.
The POS terminal needs to update the application program timely during an application process, and while the application program is being updated, the security of the data transmission should be considered. Furthermore, some POS terminals only support MODEM (modulator-demodulator unit) communication, and the download speed is pretty low when the application program is being updated. Therefore, an optimized updating method is required to ensure secure data transmission and increase the updating speed of the application program at the same time under the condition of limited network resources.